Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $43.71   9.160%   $47.7138   $47.71   $47.70   $47.70  
  Purchase #2 $193.75   12.354%   $217.6859   $217.69   $217.70   $217.70  
  Purchase #3 $157.70   10.225%   $173.8248   $173.82   $173.80   $173.80  
  Purchase #4 $207.92   4.752%   $217.8004   $217.80   $217.80   $217.80  
  Purchase #5 $222.94   10.838%   $247.1022   $247.10   $247.10   $247.10  
  Purchase #6 $167.82   12.739%   $189.1986   $189.20   $189.20   $189.20  
  Purchase #7 $182.73   6.469%   $194.5508   $194.55   $194.55   $194.60  
  7 purchase totals = $1,176.57       $1,287.8765   $1,287.87   $1,287.85   $1,287.90